Systems and methods for reducing false radar detection

ABSTRACT

Methods and systems for distinguishing between radar signals and Wi-Fi signals are provided. When a set of electromagnetic signals are received, various tests are performed on the signals to determine if the signals are associated with radar pulses or if the signals are more likely to be associated with stray WI-Fi signals or other non-radar interference. One such test relies on the relatively small variance of frequencies used by radar pulses when compared to the high variation of Wi-Fi signals. Another test relies on the relatively low peak to average power ratio of signals associated with radar pulses when compared to Wi-Fi signals. The tests described herein are an improvement on existing methods for distinguishing radar signals from Wi-Fi signals and result in less switching of Wi-Fi channels due to erroneously detected radar signals.

BACKGROUND

Dynamic Frequency Selection (DFS) is a channel allocation schemespecified for wireless LAN, commonly known as Wi-Fi. It is designed toprevent electromagnetic interference with other usages of the C bandfrequency band that had predated Wi-Fi, such as military radar,satellite communication, and weather radar. In general, when a wirelessdevice, such as an access point, is communicating over a channel of theC band frequency using Wi-Fi, the device monitors for radar or othercommunications on the channel. In the event that a radar communicationis detected, the device must announce a new channel that the device willcommunicate on and must immediately cease communicating on the channelin which the radar communication was detected.

While DFS has been successful in preventing interference between Wi-Fiand the other usages of the C band frequencies, current methods fordetecting radar or other communications is subject to false alarms. Inparticular, Wi-Fi communications, such as stray signals orcommunications in different channels, can be misinterpreted as radarcommunications. These false detections can result in unnecessarydisruptions of network communications as access points and theirassociated clients are forced to reconnect on a different channel inresponse to each false detection.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of illustrative embodiments is betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the embodiments, there is shown in the drawingsexample constructions of the embodiments; however, the embodiments arenot limited to the specific methods and instrumentalities disclosed. Inthe drawings:

FIG. 1 is an illustration of an exemplary Wi-Fi device;

FIG. 2 is an operational flow of an implementation of a method fordeterminizing if a set of electromagnetic signals is associated with aradar pulse using the variance test;

FIG. 3 is an operational flow of an implementation of a method fordeterminizing if a set of electromagnetic signals is associated with aradar pulse using the PAR test; and

FIG. 4 shows an exemplary computing environment in which exampleembodiments and aspects may be implemented.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

The following presents a simplified overview of the example embodimentsin order to provide a basic understanding of some aspects of the exampleembodiments. This overview is not an extensive overview of the exampleembodiments. It is intended to neither identify key or critical elementsof the example embodiments nor delineate the scope of the appendedclaims. Its sole purpose is to present some concepts of the exampleembodiments.

Methods and systems for distinguishing between radar signals and Wi-Fisignals are provided. When a set of electromagnetic signals arereceived, various tests are performed on the signals to determine if thesignals are associated with radar pulses or if the signals are morelikely to be associated with stray WI-Fi signals or other non-radarinterference. One such test relies on the relatively small variance offrequencies used by radar pulses when compared to the high variation ofWi-Fi signals. Another test relies on the relatively low peak to averagepower ratio of signals associated with radar pulses when compared toWi-Fi signals. The tests described herein are an improvement on existingmethods for distinguishing radar signals from Wi-Fi signals and resultin less switching of Wi-Fi channels due to erroneously detected radarsignals.

In an embodiment, a method is provided. The method includes: whilecommunicating on a first channel, receiving a set of electromagneticsignals by a computing device; estimating frequencies for the set ofelectromagnetic signals by the computing device; calculating a varianceof the estimated frequencies by the computing device; based on thecalculated variance, determining whether the set of electronic signalsare radar signals by the computing device; and if it is determined thatthe set of electronic signals are not radar signals, continuing tocommunicate on the first channel by the computing device.

Embodiments may include some or all of the following features. Themethod may further include: if it is determined that the set ofelectronic signals are radar signals: stopping communication on thefirst channel; selecting a second channel; and communicating on thesecond channel. The first communication channel may be a DFS Wi-Fichannel. The computing device may be an access point. Determiningwhether the set of electronic signals are radar signals may includedetermining whether the calculated variance satisfies a variancethreshold. The calculated variance may satisfy the variance thresholdwhen the calculated variance is less than the variance threshold. Themethod may further include: calculating a power for each electromagneticsignal of the set of electromagnetic signals; determining a peak powerfrom the calculated powers; determining an average power from thecalculated powers; based on the determined average power and thedetermined peak power, determining whether the set of electronic signalsare radar signals. Determining whether the set of electronic signals areradar signals may include: calculating a ratio of the calculated peakpower to the calculated average power; and determining whether thecalculated ratio satisfies a ratio threshold. The calculated ratio maysatisfy the ratio threshold when the calculated ratio is less than theratio threshold. The set of electromagnetic signals may include one ormore of on-channel and off-channel corrupted Wi-Fi frames or off-channelpower leaks.

In an embodiment, a method is provided. The method includes: whilecommunicating on a first channel, receiving a set of electromagneticsignals by a computing device; calculating a power for eachelectromagnetic signal of the set of electromagnetic signals by thecomputing device; determining a peak power from the calculated powers bythe computing device; determining an average power from the calculatedpowers by the computing device; based on the determined average powerand the determined peak power, determining whether the set of electronicsignals are radar signals by the computing device; and if it isdetermined that the set of electronic signals are not radar signals,continuing to communicate on the first channel by the computing device.

Embodiments may include some or all of the following features. Themethod may further include: If it is determined that the set ofelectronic signals are radar signals: stopping communication on thefirst channel; selecting a second channel; and communicating on thesecond channel. The first communication channel may be a DFS Wi-Fichannel. The computing device may be an access point. Determiningwhether the set of electronic signals are radar signals may include:calculating a ratio of the calculated peak power to the calculatedaverage power; and determining whether the calculated ratio satisfies aratio threshold. The calculated ratio may satisfy the ratio thresholdwhen the calculated ratio is less than the ratio threshold. The methodmay further include: estimating frequencies for the set ofelectromagnetic signals; calculating a variance of the estimatedfrequencies; and based on the calculated variance, determining whetherthe set of electronic signals are radar signals. Determining whether theset of electronic signals are radar signals may include determiningwhether the calculated variance satisfies a variance threshold. Thecalculated variance may satisfy the variance threshold when thecalculated variance is less than the variance threshold. The set ofelectromagnetic signals may include one or more of on-channel andoff-channel corrupted Wi-Fi frames or off-channel power leaks.

EXAMPLE EMBODIMENTS

This description provides examples not intended to limit the scope ofthe appended claims. The figures generally indicate the features of theexamples, where it is understood and appreciated that like referencenumerals are used to refer to like elements. Reference in thespecification to “one embodiment” or “an embodiment” or “an exampleembodiment” means that a particular feature, structure, orcharacteristic described is included in at least one embodimentdescribed herein and does not imply that the feature, structure, orcharacteristic is present in all embodiments described herein.

FIG. 1 is an illustration of an exemplary Wi-Fi device 110. As shown,the Wi-Fi device 110 may include one or more antennas 105 that arecapable of receiving and transmitting information via electromagneticsignals 120. As part of the Wi-Fi standard, the Wi-Fi device 110 maycommunicate information with other Wi-Fi devices (not shown) using oneof a plurality of channels. Each channel may be associated with adifferent frequency range of electromagnetic signals 120.

As used herein, a Wi-Fi device 110 may be any device that is capable ofcommunication (i.e., receiving or transmitting) using any of the Wi-Fistandard protocols. Examples include, but are not limited to, routers,access points, mobile phones, laptop or desktop computers, video gameconsoles, and other connected deices (e.g., thermostats, cameras,sensors, lights, and doorbells). The Wi-Fi device 110 may be implementedusing one or more general purpose computing devices such as thecomputing device 400 illustrated with respect to FIG. 4 .

To increase the number of channels available for communication, theWi-Fi device 110 is permitted to communication using what are referredto as dynamical frequency selection (“DFS”) channels. The DFS channelsuse electromagnetic frequencies that had been previously reserved foruse by radar, such as military radar, satellite communications, andweather radar. The particular DFS channels and associated frequenciesvaries by country.

While the use of DFS channels reduces overall channel congestion, thereare requirements and burdens associated with the use of such channels.In particular, when using a DFS channel, if the Wi-Fi device 110 detectsan electromagnetic signal 120 associated with radar, the Wi-Fi device110 must immediately stop using the DFS channels and select a newchannel for communication. Any devices that were communicating with theWi-Fi device 110 using the DFS channel will be disconnected and will beforced to reconnect with the Wi-Fi device 110 on the new channel.

One drawback with such as approach is that some non-radarelectromagnetic signals 120 received by the antenna 105 may be similarto radar signals and may cause the Wi-Fi device 110 to unnecessarilyswitch channels. Examples of such signals include Wi-Fi signals leakedfrom channels adjacent to the current DFS channel and corrupted Wi-Fisignals or headers.

In order to reduce the number of falsely detected radar signals, whenelectromagnetic signals 120 are received that include one or more pulsesthat could be associated with radar, the Wi-Fi device 110 may performone or more verification tests on received pulses to determine if theyare likely associated with radar. When the one or more tests determinethat the received pulses are not associated with radar, then they can beignored by the Wi-Fi device 110. When the one or more tests determinethat the received pulses may be associated with radar, the Wi-Fi device110 may switch channels. Depending on the embodiment, a set ofelectromagnetic signals 120 may be associated with radar when there isno Wi-Fi header.

One such verification test is referred to herein as the peak to averagepower ratio (PAR) test. One property associated with real radar pulsesis that there signals have relatively uniform power. Thus, if a set ofelectromagnetic signals 120 are associated with radar, the PAR ratio(i.e., peak or max signal power/mean signal power) for the signals 120should be relatively low. Conversely, if a set of electromagneticsignals 120 have a relatively high PAR ratio, then they are unlikely tobe associated with radar.

As part of the PAR test, when a set of electromagnetic signals 120 isreceived by the Wi-Fi device 110, the Wi-Fi device 110 computes thepower of each received signal, and using the computed powers, computesthe average power of the set of electromagnetic signals 120. Any methodfor computing signal power may be used. In some embodiments, the averagepower may be the mean power, although other types of averages may beused.

After or before computing the average power, the Wi-Fi device 110 mayfurther compute the peak power for the set of electromagnetic signals120. The peak power may be the highest computed power for any signalfrom the set of electromagnetic signals 120.

The Wi-Fi device 110 may compute the PAR for the set of electromagneticsignals and may determine if the set of electromagnetic signals 120 isor is not likely to be associated with radar. In some embodiments, theWi-Fi device 110 may make the determination using what is referred to asa PAR threshold. In general, PAR of a signal is a function of modulationtype it uses. Specifically for WiFi that uses OFDM modulation a typicalPAR range is between 12 and 15 dB. While for the most radar signals PARrange is between 3 and 5 dB.

Accordingly, the PAR threshold may be selected such that a set ofelectromagnetic signals whose PAR is above the PAR threshold is likelyto be not associated with radar, and a set of electromagnetic signalswhose PAR is below the PAR threshold is likely to be associated withradar. The PAR threshold may be empirically determined based on observedradar signals and may be set by a user or administrator. An example PARthreshold is 12 db.

Another test that may be used to distinguish radar relatedelectromagnetic signals 120 and non-radar related electromagneticsignals 120, is referred to herein as the variance test. In general, thevariance test measures the overall difference in frequencies of theelectromagnetic signals 120 in the in the set of electromagnetic signals120. With respect to radar signals, the signals in a radar pulse tend tobe more focused in frequency than electromagnetic signals 120 associatedwith a Wi-Fi signal which tend to have a wide range of frequencies.Thus, if the variance of the frequencies of the set of frequencies 120is relatively low then the set of frequencies is likely to be a radarpulse, and if the variance of the frequencies of the set of frequenciesis relatively high, then the set of frequencies is likely to beassociated with Wi-Fi.

As part of the variance test, when a set of electromagnetic signals 120is received by the Wi-Fi device 110, the Wi-Fi device 110 determines thefrequency of each signal in the set of signals 120. Any method fordetermining the frequency of a received signal may be used.

In some embodiment, the Wi-Fi device may calculate or estimate thefrequency of a signal using the following equation 1:

$\begin{matrix}{{F(n)} = \frac{{{angle}{}\left( {{s\lbrack n\rbrack}*{{conj}\left( {s\left\lbrack {n + 1} \right\rbrack} \right)}} \right)}*F_{s}}{2\pi}} & (1)\end{matrix}$

The Wi-Fi device 110 may then calculate the variance of the frequenciesof the electromagnetic signals. Any method for calculating a variancemay be used.

Once the variance has been calculated, the Wi-Fi device 110 may comparethe calculated variance to what is referred to as a variance threshold.If the calculated variance is above the variance threshold, then the setof electromagnetic signals 120 are likely associated with Wi-Fi and arenot associated with a radar pulse. If the calculated valiance is belowthe variance threshold, then the set of electromagnetics signals 120 arelikely associated with a radar pulse. Similar to the PAR threshold, thevariance threshold may be empirically determined and may be set by auser or administrator.

In some embodiments, when a set of electromagnetic signals 120 arereceived, before performing either of the verification tests (e.g., thePAR or variance test), the the Wi-Fi device 110 may further cut orremove portions of the electromagnetic signals that are above athreshold. The portions may be cut or removed using a power gate, forexample.

The Wi-Fi device 110 may perform some or both of the PAR and variancetests on a set of electromagnetic signals 120 that are suspected ofbeing associated with a radar pulse. In some embodiments, a set ofelectromagnetic signals 120 is considered to be associated with radarwhen it passes either of the PAR and variance tests. For example, a setof electromagnetic signals 20 may fail the PAR test (i.e., may bedetermined not to be associated with radar), but may pass the variancetest (i.e., may be determined to be associated with radar). In such anembodiment, the set of electronic signals 120 may be determined to beassociated with radar because it passed just one of the tests.

In other embodiments, a set of electromagnetic signals 120 is consideredto be associated with radar when it passes both of the PAR and variancetests. For example, a set of electromagnetic signals 20 may fail the PARtest (i.e., may be determined not to be associated with radar), but maypass the variance test (i.e., may be determined to be associated withradar). In such an embodiment, the set of electronic signals 120 may bedetermined to be not associated with radar because it did not pass bothof the tests.

FIG. 2 is an operational flow of an implementation of a method 200 fordeterminizing if a set of electromagnetic signals is associated with aradar pulse. The method 200 may be implemented by the Wi-Fi device 110.The method 200 may implement the variance test described above.

At 205, a set of electromagnetic signals is received. The set ofelectromagnetic signals 120 may be received by the Wi-Fi device 110 viaone or more antennae 105. Depending on the embodiment, the Wi-Fi device110 may suspect that the set of electromagnetic signals 120 isassociated with a radar pulse. The Wi-Fi device 110 may be communicatingwith one or more other Wi-Fi devices using a DFS channel. In someembodiments, the set of electromagnetic signals 120 may be cut using oneor more thresholds by a power gate.

At 210, frequencies are estimated. The frequencies of the signals areestimated by the Wi-Fi device 110. Any method for estimating frequenciesmay be used. In some embodiments, the frequencies may be estimated usingthe equation 1 described above.

At 215, a variance of the estimated frequencies is calculated. Thevariance may be calculated by the Wi-Fi device 110 using the estimatedfrequencies. Any method for calculating a variance may be used.

At 220, whether the calculated variance satisfies a threshold isdetermined. Whether the calculated variance satisfies the variancethreshold may be determined by the Wi-Fi device 110. In someembodiments, the variance threshold may be satisfied when the calculatedvariance is less than the variance threshold. If the variance thresholdis not satisfied, then the set of electromagnetic signals 120 are notassociated with a radar pulse and the method 200 may continue at 205where a next set of electromagnetic signals 120 may be considered (i.e.,a next pulse). Else, the method 200 may continue at 225.

At 225, a new channel is selected. The new channel may be selected bythe Wi-Fi device 110. Because the variance threshold was satisfied, theset of electromagnetic signals 120 is likely to be associated with aradar pulse, and therefore the Wi-Fi device 110 must immediately stopusing the DFS channel and must select a new channel for broadcasting.The selected channel may be a different DFS channel or may be a non-DFSchannel. Any method for selecting a channel may be used.

At 230, communication on the selected channel may start. Thecommunication may be started by the Wi-Fi device 110. The method 200 maythen return to 205 and wait for a next set of signals 120 to be receivedfor testing.

FIG. 3 is an operational flow of an implementation of a method 300 fordeterminizing if a set of electromagnetic signals is associated with aradar pulse. The method 300 may be implemented by the Wi-Fi device 110.The method 300 may implement the PAR test described above.

At 305, a set of electromagnetic signals is received. The set ofelectromagnetic signals 120 may be received by the Wi-Fi device 110 viaone or more antennae 105. Depending on the embodiment, the Wi-Fi device110 may suspect that the set of electromagnetic signals 120 isassociated with a radar pulse. The Wi-Fi device 110 may be communicatingwith one or more other Wi-Fi devices using a DFS channel. In someembodiments, the set of electromagnetic signals 120 may be cut using oneor more thresholds by a power gate.

At 310, a power is calculated for each signal. The power of each signalmay be calculated by the Wi-Fi device 110. Any method for calculatingpower may be used. In some embodiments, the frequencies may be estimatedusing the equation 1 described above.

At 315, peak and average power are calculated. The peak power andaverage power may be calculated by the Wi-Fi device 110 based on thecalculated powers for each signal of the set of electromagnetic signals120. Any method for calculating peak and average signal may be used.

At 320, whether a ratio of the determined peak power and average powersatisfies a threshold is determined. Whether the PRA ratio satisfies thePAR threshold may be determined by the Wi-Fi device 110. In someembodiments, the PAR threshold may be satisfied when the PAR ratio isless than the PAR threshold. If the PAR threshold is not satisfied, thenthe set of electromagnetic signals 120 are not associated with a radarpulse and the method 300 may continue at 305 where a next set ofelectromagnetic signals 120 may be considered (i.e., a next pulse).Else, the method 300 may continue at 325.

At 325, a new channel is selected. The new channel may be selected bythe Wi-Fi device 110. Because the variance threshold was satisfied, theset of electromagnetic signals 120 is likely to be associated with aradar pulse, and therefore the Wi-Fi device 110 must immediately stopusing the DFS channel and must select a new channel for broadcasting.The selected channel may be a different DFS channel or may be a non-DFSchannel. Any method for selecting a channel may be used.

At 330, communication on the selected channel may start. Thecommunication may be started by the Wi-Fi device 110. The method 300 maythen return to 305 and wait for a next set of signals 120 to be receivedfor testing.

FIG. 4 shows an exemplary computing environment in which exampleembodiments and aspects may be implemented. The computing deviceenvironment is only one example of a suitable computing environment andis not intended to suggest any limitation as to the scope of use orfunctionality.

Numerous other general purpose or special purpose computing devicesenvironments or configurations may be used. Examples of well-knowncomputing devices, environments, and/or configurations that may besuitable for use include, but are not limited to, personal computers,server computers, handheld or laptop devices, multiprocessor systems,microprocessor-based systems, network personal computers (PCs),minicomputers, mainframe computers, embedded systems, distributedcomputing environments that include any of the above systems or devices,and the like.

Computer-executable instructions, such as program modules, beingexecuted by a computer may be used. Generally, program modules includeroutines, programs, objects, components, data structures, etc. thatperform particular tasks or implement particular abstract data types.Distributed computing environments may be used where tasks are performedby remote processing devices that are linked through a communicationsnetwork or other data transmission medium. In a distributed computingenvironment, program modules and other data may be located in both localand remote computer storage media including memory storage devices.

With reference to FIG. 4 , an exemplary system for implementing aspectsdescribed herein includes a computing device, such as computing device400. In its most basic configuration, computing device 400 typicallyincludes at least one processing unit 402 and memory 404. Depending onthe exact configuration and type of computing device, memory 404 may bevolatile (such as random access memory (RAM)), non-volatile (such asread-only memory (ROM), flash memory, etc.), or some combination of thetwo. This most basic configuration is illustrated in FIG. 4 by dashedline 406.

Computing device 400 may have additional features/functionality. Forexample, computing device 400 may include additional storage (removableand/or non-removable) including, but not limited to, magnetic or opticaldisks or tape. Such additional storage is illustrated in FIG. 4 byremovable storage 408 and non-removable storage 410.

Computing device 400 typically includes a variety of computer readablemedia. Computer readable media can be any available media that can beaccessed by the device 600 and includes both volatile and non-volatilemedia, removable and non-removable media.

Computer storage media include volatile and non-volatile, and removableand non-removable media implemented in any method or technology forstorage of information such as computer readable instructions, datastructures, program modules or other data. Memory 404, removable storage408, and non-removable storage 410 are all examples of computer storagemedia. Computer storage media include, but are not limited to, RAM, ROM,electrically erasable program read-only memory (EEPROM), flash memory orother memory technology, CD-ROM, digital versatile disks (DVD) or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store the desired information and which can be accessed bycomputing device 400. Any such computer storage media may be part ofcomputing device 400.

Computing device 400 may contain communication connection(s) 412 thatallow the device to communicate with other devices. Computing device 400may also have input device(s) 414 such as a keyboard, mouse, pen, voiceinput device, touch input device, etc. Output device(s) 416 such as adisplay, speakers, printer, etc. may also be included. All these devicesare well known in the art and need not be discussed at length here.

It should be understood that the various techniques described herein maybe implemented in connection with hardware components or softwarecomponents or, where appropriate, with a combination of both.Illustrative types of hardware components that can be used includeField-programmable Gate Arrays (FPGAs), Application-specific IntegratedCircuits (ASICs), Application-specific Standard Products (ASSPs),System-on-a-chip systems (SOCs), Complex Programmable Logic Devices(CPLDs), etc. The methods and apparatus of the presently disclosedsubject matter, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as floppy diskettes, CD-ROMs, hard drives, or any othermachine-readable storage medium where, when the program code is loadedinto and executed by a machine, such as a computer, the machine becomesan apparatus for practicing the presently disclosed subject matter.

Although exemplary implementations may refer to utilizing aspects of thepresently disclosed subject matter in the context of one or morestand-alone computer systems, the subject matter is not so limited, butrather may be implemented in connection with any computing environment,such as a network or distributed computing environment. Still further,aspects of the presently disclosed subject matter may be implemented inor across a plurality of processing chips or devices, and storage maysimilarly be effected across a plurality of devices. Such devices mightinclude personal computers, network servers, and handheld devices, forexample.

The present invention has been explained with reference to specificembodiments. For example, while embodiments of the present inventionhave been described as operating in connection with IEEE 802.3 networks,the present invention can be used in connection with any suitable wirednetwork environment. Other embodiments will be evident to those ofordinary skill in the art.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed:
 1. A method comprising: while communicating on a firstchannel, receiving a set of electromagnetic signals by a computingdevice; estimating frequencies for the set of electromagnetic signals bythe computing device; calculating a variance of the estimatedfrequencies by the computing device; based on the calculated variance,determining whether the set of electronic signals are radar signals bythe computing device; and if it is determined that the set of electronicsignals are not radar signals, continuing to communicate on the firstchannel by the computing device.
 2. The method of claim 1, furthercomprising if it is determined that the set of electronic signals areradar signals: stopping communication on the first channel; selecting asecond channel; and communicating on the second channel.
 3. The methodof claim 1, wherein the first communication channel is a DFS Wi-Fichannel.
 4. The method of claim 1, wherein the computing device is anaccess point.
 5. The method of claim 1, wherein determining whether theset of electronic signals are radar signals comprises determiningwhether the calculated variance satisfies a variance threshold.
 6. Themethod of claim 5, wherein the calculated variance satisfies thevariance threshold when the calculated variance is less than thevariance threshold.
 7. The method of claim 1, further comprising:calculating a power for each electromagnetic signal of the set ofelectromagnetic signals; determining a peak power from the calculatedpowers; determining an average power from the calculated powers; basedon the determined average power and the determined peak power,determining whether the set of electronic signals are radar signals. 8.The method of claim 7, wherein determining whether the set of electronicsignals are radar signals comprises: calculating a ratio of thecalculated peak power to the calculated average power; and determiningwhether the calculated ratio satisfies a ratio threshold.
 9. The methodof claim 8, wherein the calculated ratio satisfies the ratio thresholdwhen the calculated ratio is less than the ratio threshold.
 10. Themethod of claim 1, wherein the set of electromagnetic signals comprisesone or more of on-channel and off-channel corrupted Wi-Fi frames oroff-channel power leaks.
 11. A method comprising: while communicating ona first channel, receiving a set of electromagnetic signals by acomputing device; calculating a power for each electromagnetic signal ofthe set of electromagnetic signals by the computing device; determininga peak power from the calculated powers by the computing device;determining an average power from the calculated powers by the computingdevice; based on the determined average power and the determined peakpower, determining whether the set of electronic signals are radarsignals by the computing device; and if it is determined that the set ofelectronic signals are not radar signals, continuing to communicate onthe first channel by the computing device.
 12. The method of claim 11,further comprising if it is determined that the set of electronicsignals are radar signals: stopping communication on the first channel;selecting a second channel; and communicating on the second channel. 13.The method of claim 11, wherein the first communication channel is a DFSWi-Fi channel.
 14. The method of claim 11, wherein the computing deviceis an access point.
 15. The method of claim 11, wherein determiningwhether the set of electronic signals are radar signals comprises:calculating a ratio of the calculated peak power to the calculatedaverage power; and determining whether the calculated ratio satisfies aratio threshold.
 16. The method of claim 15, wherein the calculatedratio satisfies the ratio threshold when the calculated ratio is lessthan the ratio threshold.
 17. The method of claim 11, furthercomprising: estimating frequencies for the set of electromagneticsignals; calculating a variance of the estimated frequencies; and basedon the calculated variance, determining whether the set of electronicsignals are radar signals.
 18. The method of claim 17, whereindetermining whether the set of electronic signals are radar signalscomprises determining whether the calculated variance satisfies avariance threshold.
 19. The method of claim 18, wherein the calculatedvariance satisfies the variance threshold when the calculated varianceis less than the variance threshold.
 20. A system comprising: at leastone computing device; and a computer-readable medium storingcomputer-executable instructions that when executed by the at least onecomputing device causes the at least one computing device to: whilecommunicating on a first channel, receive a set of electromagneticsignals; estimate frequencies for the set of electromagnetic signals;calculate a variance of the estimated frequencies; based on thecalculated variance, determine whether the set of electronic signals areradar signals; if it is determined that the set of electronic signalsare not radar signals, continue to communicate on the first channel; andif it is determined that the set of electronic signals are radarsignals: stop communication on the first channel; select a secondchannel; and communicate on the second channel.